As one of such a type of plant growth apparatuses, there has been proposed a plant growth apparatus that includes a closed type growth space configured to grow plants and is provided with an air conditioning device that controls the environments such as temperature and humidity within the growth space, and an illumination device that controls the lighting within the growth space. For example, Japanese National Publication of International Publication No. 2016-507220 suggests a technique for controlling illuminance in an artificial light source as an illumination device. Japanese Patent Laid-Open Publication No. 2015-171351 proposes a technique for controlling the temperature of the growth space using an air conditioning device. Japanese Patent Laid-Open Publication No. 2014-161298 proposes a technique for controlling temperature by controlling ventilation of a growth space using an air conditioning device.
Techniques disclosed in Japanese National Publication of International Patent Application No. 2016-507220, Japanese Patent Laid-Open Publication No. 2015-171351, and Japanese Patent Laid-Open Publication No. 2014-161298 are effective as general or general-purpose plant growth apparatuses that are not limited to plant species to be grown, but are not necessarily the most suitable apparatuses for growing different plant species. That is, in different plant species, it is considered that the respective optimal growing conditions, particularly, the environmental conditions such as temperature and humidity in the growth space, and the illumination conditions such as illuminance and light color (light spectrum) of the artificial light source are different from each other.
Therefore, test apparatuses for finding the optimal growing conditions for each of different plant species are considered. For example, the optimal growing conditions for each plant species can be obtained by configuring a test apparatus capable of observing the growing state of plants by changing and controlling the various growing conditions disclosed in Japanese National Publication of International Patent Application No. 2016-507220, Japanese Patent Laid-Open Publication No. 2015-171351, and Japanese Patent Laid-Open Publication No. 2014-161298. However, since the techniques disclosed in Japanese National Publication of International Patent Application No. 2016-507220, Japanese Patent Laid-Open Publication No. 2015-171351, and Japanese Patent Laid-Open Publication No. 2014-161298 are configurations in which illumination devices are fixedly provided inside the growth space, the change and control of the illumination conditions are restricted. In particular, it is very difficult to change and control the optical spectrum under the same light source. In order to realize the change and control, it is necessary to replace the entire light source or illumination device with one having different standards, and the work for doing this becomes complicated.
Further, the techniques disclosed in Japanese National Publication of International Patent Application No. 2016-507220 and Japanese Patent Laid-Open Publication No. 2015-171351 have a limitation in terms of the controlled speed at the time of changing the environmental conditions of the growth space since the air conditioning device is integrally provided with respect to the plant growth apparatus. Especially, since it is difficult to change and control the environmental conditions of the growth space instantaneously, a time lag occurs until a test for another plant species is started, and as a result, the test time is lengthened. In addition, when a large capacity air conditioner is used, it is possible to increase the controlled speed. However, the test apparatus provided with such an air conditioning device becomes large and expensive.
An object of the present disclosure is to provide a plant growth apparatus configured to expand the range of change and control of illumination conditions in a growth space with a simple operation. Another object of the present disclosure is to provide a plant growth apparatus configured to rapidly change and control the environmental conditions of the growth space.